Wireless communication devices typically feature a transmitter chip that drives an antenna. The antenna may be integrated inside the transmitter chip, but more commonly the transmitter chip and the antenna are integrated onto a module or other device.
Various Automated-Test-Equipment (ATE) have been developed to test chips such as transmitter chips. ATE may be connected to a horn antenna to directly measure electro-magnetic radiation emitted by the antenna.
FIG. 1 shows a horn antenna connected to an ATE to test for emitted electromagnetic radiation from a transceiver. Interface board 120 connects between ATE 128 and Device-Under-Test (DUT) transceiver 100, which may be placed into a socket (not shown) on interface board 120.
During testing, ATE 128 or other test instruments sends out stimulus or input signals that are routed though interface board 120 to the inputs of DUT transceiver 100. Electrical outputs from DUT transceiver 100 are routed through interface board 120 to ATE 128, which may perform various electrical tests such as for shorts, opens, power-supply current, programming registers, modes, and receiver and other functions. However, a primary function of DUT transceiver 100 is to drive an antenna (not shown) to emit electromagnetic radiation such as Radio-Frequency (RF) waves. The antenna may be part of a module that forms DUT transceiver 100 along with a transceiver integrated circuit (IC).
When ATE 128 activates DUT transceiver 100 to transmit, electromagnetic radiation waves 144 are emitted from the antenna in DUT transceiver 100. These waves 144 travel away from DUT transceiver 100. The radiated signal intensity and the physical geometry of the antenna causes electromagnetic radiation waves 144 to have a pattern that may generally be described as having an envelope 114 where radiation intensities within envelope 114 are above a threshold amount, such as to be detectable by a receiver. Envelope 114 may be a free space envelope around DUT transceiver 100 or may be modified by structures, such as of metal, plastic, or dissipative materials placed near the transceiver.
Horn antenna 102 may be placed within envelope 114 to receive these waves 144. Horn antenna 102 has flaring metal sides shaped like a horn that allow horn antenna 102 to collect electromagnetic radiation. A detector at the rear of the horn receives the electromagnetic radiation that bounces off the flared sides of the horn and into the back of the horn. This detector converts the electromagnetic radiation into electrical signals that are sent to ATE 128 to evaluate the intensity of the electromagnetic radiation transmitted from DUT transceiver 100.
Horn antennas are especially useful for radio waves above 300 MHz. However, they tend to be large in size and bulky. Typically DUT transceiver 100 is much smaller than horn antenna 102. Physically placing a large horn antenna 102 near DUT transceiver 100 is challenging or impossible in many test environments. Thus using a large horn antenna may not be practical.
FIG. 2 shows a radiation chamber in a test environment. Some DUT transceivers 100 may transmit with a very small power. DUT transceiver 104 on interface board 120 transmits with a very low power so that emitted electromagnetic radiation waves 144 form a smaller envelope 116. Due to the small radiated power from the DUT transmitter 104 and the practical sizes of horn antenna 102, horn antenna 102 may not be able to adequately receive the transmitted signal. Radiation chamber 122 helps contain the radiation and direct it to horn antenna 102. Radiation chamber 122 also blocks unwanted noise radiation from reaching horn antenna 102. Noise radiation may arise in an ATE test environment from the high-speed signals sent to interface board 120 or within or surrounding ATE 128.
An opening in radiation chamber 122 is placed over DUT transceiver 104 to receive smaller envelope 116. Electromagnetic radiation waves 144 may bounce off the metal walls of radiation chamber 122 until waves 144 reach horn antenna 102. A detector in the rear of horn antenna 102 converts these electromagnetic radiation waves into electrical signals that are sent to ATE 128 for evaluation.
While radiation chamber 122 may extend the range of horn antenna 102, there are still limits caused by the small radiated power of DUT transceiver 104. The amount of electromagnetic radiation waves 144 that finally reach the detector in the rear of horn antenna 102 may be too low to accurately measure the emitted radiation from DUT transceiver 104. The electromagnetic radiation may be attenuated too much by multiple bounces off of non-ideal walls within radiation chamber 122. Radiation chamber 122 may be too long or too bulky to use in a test environment.
A typical RF receiver that is optimized for communication over distances in the meter to kilometer range is unlikely to be able to accurately receive a signal of very low power when the receiver is not in close proximity (0.1 mm to 20 mm) to the transmitter. The receiver should be optimally placed in close proximity to the low-power transmitter. The optimal placement may be from 0.1 mm to 20 mm. This is a problem since many test fixtures are large and bulky, often much greater than 20 mm in size, preventing a receiver from be placed physically close enough to the DUT transmitter being tested in the test fixture.
Lower frequencies with longer wavelengths have a larger near-field region than do higher frequency signals. Thus radio waves commonly used with Radio-Frequency Identification (RFID) have a near-field region of about a few meters, but the data rates are limited by the radio frequency to perhaps several kHz to a few MHz. Thus RFID systems tend to transmit small amounts of data, such as identifiers.
It is desired to wirelessly transmit video and other data that require high data rates. RFID is too limited by the low frequency of radio waves. The assignee has developed wireless communication systems that use Extremely High-Frequency (EHF) electromagnetic radiation rather than using Radio-Frequency (RF) electromagnetic radiation. EHF radiation has a frequency in the range of 30 GHz to 300 GHz. This higher frequency allows for data rates as much as 1,000 times faster than with RF transmissions in the MHz range. However, the wavelength of radiation is much smaller than for current RFID systems.
Horn antenna 102 may be too bulky to be placed within 1-2 cm of DUT transceiver 104. Horn antenna 102 may also cause undesirable loading effects on the transmitter and may even shift its transmitted frequency. Thus testing EHF transceivers is problematic. The amount of energy that may be transmitted from an antenna driven by a small IC such as used in DUT transceiver 104 may be so small that a typical receiver would not be able to adequately pick up the transmitted signal at a distance of greater than 20 mm.
What is desired is a test system that collects and detects electromagnetic radiation. A test fixture that is able to direct radiation to and from the DUT to a location outside the test fixture is desired. A test method that can collect small amounts of radiation that are only detectable within a few centimeters of the transmitting antenna is desired. A low-cost method to collect small amounts of radiation emitted from a transmitter is desirable. An EHF near-field radiation collector that can be added to an ATE is also desirable.